WO2020225951A1

WO2020225951A1 - Apparatus for producing radionuclide and method for producing radionuclide

Info

Publication number: WO2020225951A1
Application number: PCT/JP2020/005352
Authority: WO
Inventors: 田所　孝広; 上野　雄一郎; 祐子可児
Original assignee: 株式会社日立製作所
Priority date: 2019-05-09
Filing date: 2020-02-12
Publication date: 2020-11-12
Also published as: US20220199277A1; EP3968342A1; EP3968342A4; JP2020183926A; EP3968342B1; JP7194637B2

Abstract

The purpose of the present invention is to efficiently produce a radionuclide.　In the present invention, while a fluid including a raw material is circulated along a circulation path, a first radionuclide is generated in the fluid from the raw material by irradiating the fluid with radiation midway along the circulation path. While the fluid is circulated along the circulation path, a substance including at least a portion from among the first radionuclide and a second radionuclide generated from the first radionuclide is then taken from the fluid, and the remaining fluid including the raw material is returned to the circulation path and recirculated.

Description

Radionuclide production equipment and radionuclide production method

The present invention relates to an apparatus for producing a radionuclide using an accelerator, and in particular, a radionuclide that emits alpha rays typified by actinium 225 (Ac-225), which is in great demand as a raw material for a therapeutic drug, is compact and lightweight. The present invention relates to a radionuclide production apparatus capable of efficiently producing the apparatus.

Actinium 225 (Ac-225), a nuclide that emits alpha rays, which has been conventionally used for research and development as a raw material nuclide for therapeutic drugs, is produced by decay from the parent nuclide, thorium 229 (Th-229). ing. Currently, the facilities that can supply clinically available Ac-225 are the Institute for Transuranium Elements (ITU) in Karlsruhe, Germany, and the Oak Ridge National Laboratory (ORNL) in the United States. And, there are only three places in the world of the Institute of Physics and Power Engineering (IPPE) of the Russian National Science Center in Obninsk, Russia.

Th-229 is not found in nature and is produced by the collapse of uranium-233 (U-233), but due to nuclear protection, U-233 will not be manufactured in the future, so the world's production capacity is currently high. , Only the amount produced by the collapse of Th-229 produced by the collapse of U-233 held in the world. Although this amount is sufficient for use in preclinical studies and the like, it is expected that a large amount will be insufficient in the future, and production using an accelerator is desired.

Regarding the production of Ac-225 using an accelerator, the naturally occurring radium-226 (Ra-226) is irradiated with cyclotron-accelerated protons, and Ra emits two neutrons for each irradiated proton. A production method using the -226 (p, 2n) Ac-225 reaction is known from Patent Document 1 and the like. In addition, tests of this manufacturing method are underway at ORNL and the National Institutes for Quantum and Radiological Science and Technology, but have not been commercialized. The manufacturing method using a cyclotron has a problem that mass production cannot be performed even if the Ra-226 target is thickened because the range of the accelerated protons in the Ra-226 target is short. In addition, this manufacturing method loses most of the accelerated proton energy in the target, which raises the temperature of the target, but it is difficult to remove the heat, so the current value and energy are improved for mass production. There are problems such as not being able to make it.

As another method for producing Ac-225 using an accelerator, the Ra-226 target is irradiated with high-speed neutrons, and two neutrons are emitted for each irradiated neutron. Ra-226 (n, 2n) Ra-225 A method for producing radium-225 (Ra-225) by the reaction and producing Ac-225 by beta decay of the obtained Ra-225 is being studied. Accelerated neutrons are generated by irradiating deuterons accelerated by a cyclotron to a carbon target or a target such as a metal that has occluded tritium. Fast neutrons have a long range in Ra-226. Therefore, by thickening the raw material Ra-226, Ac-225 can be produced in large quantities, but there is a problem that the apparatus becomes large because it is necessary to shield the fast neutrons generated in large quantities. There is also a problem that the entire device structure is strongly activated by a large amount of fast neutrons.

On the other hand, Patent Document 2 discloses a purification method in which an Ra-226 target containing Ac-225 is dissolved in nitric acid and then Ac-225 is separated and extracted from Ra-226 by chromatography.

Patent Documents 3 and 4 disclose a method of irradiating a target for braking radiation with electrons accelerated by a small electron beam accelerator to generate braking radiation (γ-rays), and irradiating the raw material with the generated braking radiation. ing. As a result, neutrons can be emitted from the raw material by the (γ, n) reaction to produce a desired radionuclide. By this production method, molybdenum 99 (Mo-99) can be produced from molybdenum 100 (Mo-100) as a raw material. Furthermore, the beta decay of Mo-99 can produce technetium-99m (Te-99m). Te-99m is used for applications such as being administered to a subject during imaging with a single-photon emission-section imaging device (SPECT).

The devices of Patent Documents 3 and 4 are configured to heat the raw material, move the vaporized technetium oxide by flowing it with a gas, and separate the participating technetium from the gas in order to take out the generated Te-99m.

Special Table 2007-508531 Japanese Unexamined Patent Publication No. 2009-527731 JP-A-2015-99117 Japanese Unexamined Patent Publication No. 2016-80574

The method of producing a desired radionuclide by irradiating the raw material target with protons or neutrons described in Patent Document 1 or the like raises the temperature of the raw material target. Therefore, it is necessary to cool the raw material target, but it is not easy to cool the raw material target while the accelerator is irradiating protons or neutrons. Therefore, it is difficult to perform continuous irradiation. Further, since the desired radionuclide is generated on the surface or inside of the raw material target such as a plate, it is necessary to take out the raw material target and dissolve it in order to extract it, and during that time, it is necessary to stop the irradiation of protons or the like. ..

Further, in the methods of Patent Documents 3 and 4, the raw material target is heated to the boiling point of the radionuclide to be taken out or higher while being placed at the position where the braking radiation is irradiated, and the vaporized radionuclide is flowed with gas to separate the radionuclide. To do. It is not easy to heat a raw material target that is being irradiated to above the boiling point of the radionuclide to be extracted. Therefore, it is difficult to extract radiation nuclides while continuously irradiating the raw material with radiation. In addition, the boiling point of the radionuclide to be extracted must be higher than the boiling point of the raw material, and the combination of the raw material and the radionuclide to be extracted is limited.

For the above reasons, it was difficult for the manufacturing methods of

Patent Documents

1, 3 and 4 to improve the manufacturing efficiency.

An object of the present invention is to efficiently produce a radionuclide.

In order to achieve the above object, the radionuclide production apparatus of the present invention irradiates a circulation path for circulating a fluid containing a raw material and at least a part of the circulation path to generate a first radionuclide from the raw material. A substance containing at least a part of the first radionuclide and the second radionuclide generated from the first radionuclide is extracted from the radiation generator and the fluid circulating in the circulation path, and the remaining raw material. It has a separation device that returns the fluid containing the above to the circulation path.

According to the present invention, by circulating the fluid containing the raw material, the raw material can be supplied to the position where the radiation is irradiated, and after the irradiation, the desired radionuclide can be separated by moving from the irradiation position to the separation device. Further, since the circulating fluid can be cooled or heated at a position different from the irradiation position to control the temperature, the radionuclide can be efficiently produced at a predetermined temperature.

It is a block diagram which shows the structure of the radionuclide production apparatus of Embodiment 1 of this invention. It is a graph which shows the theoretical value of the reaction cross section of the reaction which irradiates Ra-226 with gamma ray and generates one neutron. It is a block diagram which shows the structure of the radionuclide production apparatus of Embodiment 2 of this invention. It is a block diagram which shows the structure of the radionuclide production apparatus of Embodiment 3 of this invention. It is a block diagram which shows the structure of the radionuclide production apparatus of Embodiment 4 of this invention. This is an example of adjusting the flow rate of the pump in the radionuclide production apparatus according to the fourth embodiment of the present invention. It is a block diagram which shows the structure of the radionuclide production apparatus of Embodiment 5 of this invention. It is a block diagram which shows the structure of the radionuclide production apparatus of Embodiment 6 of this invention. It is a graph which shows an example of the amount of Ra-225 and Ac-225 in the fluid 20 when the fluid 20 containing Ra-226 is irradiated with the braking radiation 12 for 20 hours shorter than the half-life of Ra-225. .. Ra-225 and Ac in the fluid 20 when the fluid 20 containing Ra-226 is irradiated with braking radiation 12 for 20 hours, which is shorter than the half-life of Ra-225, and then Ac-225 is intermittently separated. It is a graph which shows an example of the amount of -225. It is a figure explaining the example of moving the circulation loop 21 of the radionuclide production apparatus of Embodiment 6 of this invention, and producing another raw material nuclide 15.

An embodiment of the present invention will be described.

As shown in FIG. 1, the radionuclide production apparatus of the present embodiment includes a circulation path 21 for circulating a fluid 20 containing a raw material, a radiation generator 50, and a separation apparatus 30.

In the present embodiment, the manufacturing apparatus irradiates the fluid 20 with radiation 12 from the radiation generator 50 in the middle of the circulation path while circulating the fluid 20 containing the raw material along the circulation path 21, and the raw material in the fluid 20. Produces a first radionuclide from. Further, while the fluid 20 is circulated along the circulation path 21, the separator 30 uses at least one of the first radionuclide and the second radionuclide generated from the first radionuclide in the fluid 20. The substance containing the portion is taken out, and the fluid 20 containing the remaining raw materials is returned to the circulation path and circulated.

As described above, in the present embodiment, the raw material is circulated while the fluid 20 containing the raw material is circulated, the raw material is irradiated in the middle of the circulation, the desired radionuclide is taken out, and the remaining raw material is returned to the circulation path again. While constantly circulating the containing fluid 20, radiation can be continuously irradiated to generate a desired radionuclide, and the generated radionuclide can be taken out from the fluid 20. Therefore, the production efficiency of radionuclides can be improved.

Further, although the radionuclide production apparatus of the present embodiment has a simple structure, the raw material that has not been converted into the radionuclide can be repeatedly circulated. Therefore, the circulation path serves as a supply mechanism for the raw material and the radionuclide. Since it also functions as a moving mechanism for taking out the radionuclide and also as a storage mechanism for raw materials and generated radionuclides, the device configuration can be simplified.

Further, in the radionuclide production apparatus of the present embodiment, since the fluid 20 can be constantly circulated, it is possible to prevent an excessive temperature rise of the raw material due to irradiation. Further, since the cooling device and the heating device of the fluid 20 can be easily arranged in the region where the radiation is not irradiated in the middle of the circulation path, it is easy to cool or heat the temperature of the fluid 20 to a desired temperature. Can be done.

Further, in the radionuclide production apparatus of the present embodiment, the production amount of the radionuclide can be easily adjusted by adjusting the circulation speed of the fluid 20 and the concentration of the raw material contained in the fluid 20 and adjusting the extraction amount of the radionuclide. can do.

The radiation generator 50 may be any device as long as it can irradiate the fluid 20 with radiation, and for example, an accelerator that accelerates charged particles can be used. Specifically, for example, an electron beam accelerator, a cyclotron, a synchrotron, and a cyclosynchrotron can be used. Of these, the electron beam accelerator that emits the accelerated electron beam is suitable for a small radionuclide production apparatus because it can be made smaller and simpler than other accelerators. In particular, a linear electron beam accelerator is suitable because of its small size.

For example, the radiation generator 50 can use an electron beam accelerator 1 and a holding unit 11a that holds the braking radiation target 11 at a position where the electron beam emitted from the electron beam accelerator is irradiated. As a result, the fluid 20 can be irradiated with the braking radiation (γ-rays) 12 generated from the braking radiation target 11 irradiated with the electron beam. Therefore, by irradiating the raw material with one braking radiation (γ-ray), 1 Radionuclides can be produced from raw materials by (γ, n) reactions that generate neutrons.

As the fluid 20 circulated in the circulation path 21, for example, any one of a dissolved solution in which the raw material is dissolved in a solvent, a dispersion solution in which the raw material is dispersed in the solvent, and a dispersed gas in which the raw material is dispersed in a gas is used. be able to.

The raw material may be any material that produces radionuclides by irradiation with radiation.

For example, as a raw material, any of Ra-226 (the number after the element symbol indicates the mass number), Mo-100, Zn-68, Ge-70, Zr-91, Pd-106, and Hf-178. Or these oxides, nitrides, carbonates, hydrides, chlorides, carbides, specifically molybdenum trioxide, zinc oxide, zinc carbonate, monoxide and germanium dioxide, germanium hydride, zirconium dioxide. , Zirconium chloride, palladium hydride, hafnium chloride, hafnium carbide and the like can be used as raw materials.

When the fluid 20 is used as a dissolution solution for the raw material, any solvent that can dissolve the raw material may be used. For example, when the raw material is Ra-226, an aqueous solution, a hydrochloric acid solution, or a nitric acid solution can be used as the fluid 20.

When a dispersion solution of raw materials is used as the fluid 20, a slurry in which raw material particles are dispersed can be used by using a solvent that does not dissolve the raw materials.

When a dispersed gas is used as the fluid 20, an inert gas in which fine particles of the raw material are dispersed can be used. Further, the gas containing the vapor of the raw material may be used as the fluid 20.

Specifically, in the radionuclide production apparatus of the present embodiment, the raw material is radium-226 (Ra-226), and an aqueous solution thereof, a hydrochloric acid solution or a nitrate solution is used as the fluid 20, and a radiation generator using an electron beam accelerator is used. By irradiating with braking radiation from the source, radium-225 (Ra-225) can be generated in the fluid 20 as the first radionuclide by the (γ, n) reaction. Ra-225 decays in the fluid 20 to become actinium 225 (Ac-225) as the second radionuclide. The separation device is configured to separate actinium 225 (Ac-225) from the fluid 20.

At this time, the reaction cross section (Ra-226 (γ, n) Ra-225) of the (γ, n) reaction that produces Ra-225 from Ra-226 irradiates Ra-226 with accelerated protons, and 2 Since it is about the same as the reaction cross section of the method (Ra-226 (p, 2n) Ac-225) for directly producing Ac-225 by the reaction of emitting neutrons, the production efficiency can be maintained.

Further, in the radioactive nuclei production apparatus of the present embodiment, the raw material is molybdenum 100 (Mo-100) or molybdenum trioxide 100, the hydrochloric acid or nitrate solution thereof is used as the fluid 20, and neutron rays are irradiated from the radiation generator. , (N, 2n) reaction can generate molybdenum 99 (Mo-99) in the fluid 20 as the first radioactive nuclei. Mo-99 decays to technetium-99m (Te-99m) as the second radionuclide. In this case, the separation device 30 is configured to separate Te-99m from the fluid 20.

In the present embodiment, the separation device 30 may be any structure as long as it can extract at least a part of the first radionuclide and the second radionuclide. For example, a column filled with a stationary phase (or carrier) is used as the separation device 30, and the raw material and the first radionuclide or the second radionuclide are separated and taken out by chromatography by passing the column through the fluid 20. The configuration is such that the first radionuclide or the second radionuclide is extracted from the part 31. At this time, the liquid containing the raw material after separation is returned to the circulation loop 21 again.

Further, the separation device 30 adds a material that binds to and precipitates the first radionuclide and the second radionuclide to the fluid 20, and collects and recovers the precipitate to obtain the first radionuclide and the second radionuclide. The structure may be such that the liquid containing the raw material that has not been taken out and precipitated is returned to the circulation loop 21.

When the fluid 20 is a dispersion solution (slurry), the separator 30 heats the first radionuclide or the second radionuclide above the boiling point, recovers the vapor and cools the first radionuclide or the second radionuclide. The radionuclide may be taken out, and the solvent may be added again to the raw material that has not become vapor to return it to the circulation loop 21 as a slurry.

Further, the target 11 for braking radiation may be any one as long as it generates braking radiation by irradiation with an electron beam 10, and for example, a metal having a large atomic number such as tungsten, platinum, lead, or bismuth is used. ..

Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.

<< Embodiment 1 >>
The configuration of the radionuclide production apparatus of the first embodiment will be described with reference to FIG.

The radionuclide production apparatus of the present embodiment irradiates the target 11 for braking radiation held by the holding portion 11a with the electron beam 10 accelerated by the electron beam accelerator 1 as shown in FIG. γ-ray) 12 is generated. A pump 22 for circulating the fluid 20 and a separation device 30 for separating desired radionuclides are arranged in the middle of the circulation path (hereinafter referred to as a circulation loop) 21.

The fluid (here, the solution) 20 containing the raw material circulates in the circulation loop 21.

The fluid 20 containing the raw material is irradiated with the braking radiation 12 emitted from the braking radiation target 11 when passing through the circulation loop 21 arranged close to the braking radiation target 11. As a result, the first radionuclide is generated from the raw material nuclide in the fluid 20 by the (γ, n) reaction that generates one neutron by the irradiation of one braking radiation.

The fluid 20 containing the generated radionuclide and the raw material further moves in the circulation loop 21, and during that time, the first radionuclide partially collapses and changes to the second radionuclide. The fluid 20 reaches the separation device 30, and at least a part of the first radionuclide and the second radionuclide is taken out from the extraction unit 31 by the separation device 30. The fluid containing the first radionuclide and the second radionuclide and the raw material that have not been taken out moves again through the circulation loop 21 and is irradiated with the braking radiation 12.

The above reaction and separation are repeated each time the fluid 20 circulates in the circulation loop 21.

For example, Ra-226 can be used as a raw material, and an aqueous solution, a hydrochloric acid solution, or a nitric acid solution of the raw material can be used as the fluid 20. The fluid 20 containing the raw material Ra-226 repeatedly circulates in the circulation loop 21, and each time it is irradiated with the braking radiation 12, the raw material nuclides Ra-226 to Ra-225 in the fluid 20 are released by the (γ, n) reaction. Will be generated. The Ra-225 produced undergoes beta decay with a half-life of 14.8 days and becomes partly a progeny nuclide, Ac-225, during circulation. Therefore, the fluid 20 flowing through the circulation loop 21 includes the raw material Ra-226 and the generated Ra-225 and Ac-225.

The separation device 30 takes out Ac-225 by a column or the like.

From the above, Ac-225, which is a raw material for therapeutic agents, can be produced by the production apparatus of the present embodiment.

Fig. 2 shows the theoretical value of the reaction cross section of the reaction in which Ra-226 is irradiated with gamma rays to generate one neutron. From FIG. 2, it can be seen that Ra-225 can be generated by irradiating Ra-226 with γ-rays (radiation) 12 having an energy equal to or higher than the threshold value.

The electron beam accelerator 1 can be downsized as compared with the proton accelerator or the heavy particle accelerator if the acceleration energy and the acceleration current value are the same. The formation cross-sectional area of the (γ, n) reaction that produces Ra-225 from Ra-226 is the method of irradiating Ra-226 with accelerated protons (Ra-226 (p, 2n) Ac-225) Ac- It is comparable to the cross-sectional area that produces 225. Therefore, the radionuclide production apparatus of the present embodiment using the electron beam accelerator 1 can be made smaller than the radionuclide production apparatus using the proton accelerator or the heavy particle accelerator.

In addition, when an electronic linear accelerator is used, the neutrons generated from the braking radiation target are relatively small, and most of the braking radiation is easily shielded by lead or the like. Therefore, the braking radiation target and its surroundings are shielded. Therefore, it is possible to reduce the size of the radionuclide production apparatus.

In FIG. 1, for convenience of illustration, the electron beam accelerator 1 is shown to be smaller than the circulation loop 21, but the actual electron beam accelerator 1 has a length of several meters, whereas the circulation loop 21 has a length of several meters. The diameter of the loop can be within 1 m.

Of course, in the present embodiment, it is also possible to use a proton accelerator or a heavy particle accelerator as the radiation generator. For example, the above-mentioned (Ra-226 (p, 2n) Ac-225) reaction may be used, or the (Ra-226 (n, 2n) Ra-225) reaction may be used.

In the radionuclide production apparatus of the present embodiment, most of Ra-226, which is a raw material nuclide in the fluid 20, remains as a raw material nuclide without nuclear reaction with the braking radiation 12. Further, since it is difficult to separate and purify Ra-225 produced by the reaction between the braking radiation 12 and the raw material from Ra-226 in the separation device 30, Ra-226 and Ra-225 are fluid 20. It circulates in the state contained in. Although Ra-225 is also irradiated with braking radiation 12 each time it circulates, the amount of Ra-226 in the fluid 20 is very small compared to Ra-226, so the nuclides from Ra-225 and braking radiation. The amount of nuclides produced by the reaction is very small and does not matter.

In Ra-225, the fluid 20 undergoes beta decay while circulating in the circulation loop 21 and is transformed into Ac-225, and each time the fluid 20 passes through the separation device 30, Ac-225 is separated from the take-out unit 31. Taken out. Therefore, Ac-225 can be continuously or as needed to be taken out from the take-out unit 31, and the circulation loop 21 can also have a function of storing raw material nuclides.

Ac-225, which is useful as a raw material for therapeutic drugs, becomes Fr-221, which is a progeny nuclide, with a half-life of 10.0 days. Fr-221 becomes At-217 with a half-life of 4.9 minutes, and At-217 becomes Bi-213 with a half-life of 32 ms. Ac-225 and its progeny nuclides are useful as raw materials for therapeutic drugs, but Ra-226 and Ra-225 are unnecessary nuclides as raw materials for therapeutic drugs because they are not nuclides that emit alpha rays. , Separation and purification with Ac-225 is required. In the radiation generator of the present embodiment, Ra-226 and Ra-225 can be separated from Ac-225, circulated again, and reused.

As described above, the radiation generator of the first embodiment can efficiently produce radionuclides by irradiating the radiation while circulating the fluid containing the raw material.

<< Embodiment 2 >>
An example of the radionuclide production apparatus of the second embodiment will be described with reference to FIG.

The radionuclide production apparatus of the second embodiment has the same configuration as the apparatus of FIG. 1 of the first embodiment, but in the second embodiment, a linear region 21a is provided in the circulation loop 21, and the central axis 12a of the braking radiation 12 is formed. It differs from the first embodiment in that the radiation generator 50 is arranged so as to pass through the linear region 21a of the circulation loop 21.

The configuration of the radionuclide production apparatus of the second embodiment is larger than the case where the braking radiation is irradiated so that the distance that the braking radiation 12 passes through the fluid 20 in the circulation loop 21 crosses the circulation loop 21 as shown in FIG. Due to the lengthening, the amount of the first radionuclide produced from the raw material in the fluid 20 can be increased. As a result, the production efficiency of radionuclides can be increased. Hereinafter, it will be described in more detail.

Similar to the first embodiment, the radiation generator 50 of the second embodiment generates braking radiation by irradiating the target 11 for braking radiation with the electron beam 2 accelerated by the electron beam accelerator 1. When the target 11 for braking radiation is irradiated with an electron beam having a relatively high energy such as the electron beam 2 emitted from the electron beam accelerator 1, the central axis 12a having the highest intensity of the braking radiation 12 generated is the electron beam. It coincides with the irradiation axis direction of.

Therefore, in the device of the second embodiment, a part of the circulation loop 21 (straight line region 21a) is installed so that its longitudinal direction coincides with the central axis 12a where the braking radiation 12 is strongly generated.

The range of the braking radiation 12 in the fluid (solution) 20 containing the raw material is very long as compared with the range of charged particles such as protons or deuterons. Therefore, by installing a part of the circulation loop 21 (straight line region 21a) so that the longitudinal direction thereof coincides with the central axis 12a of the braking radiation 12, the amount of reaction between the raw material nuclide in the circulation loop 21 and the braking radiation can be increased. To increase. Therefore, when the fluid 20 contains Ra-226 as a raw material as in the example described in the first embodiment, the amount of Ra-225 produced by the manufacturing apparatus of the second embodiment is larger than that of the manufacturing apparatus of the first embodiment. To increase.

In the present embodiment, the circulation loop 21 is provided with a linear region 21a so that the longitudinal direction coincides with the central axis 12a of the braking radiation 12, but the configuration is not limited to this, and the braking radiation 12 circulates. It is possible to provide another structure in the circulation loop 21 for increasing the distance through the loop 21. For example, the intensity distribution of the braking radiation 12 is the strongest in the axial direction (central axis 12a) of the electron beam 10 centering on the position where the electron beam 10 irradiates the target 11 for braking radiation, and the angle formed by the central axis 12a. The diameter of the circulation loop 21 may be increased in the direction of the central axis 12a because it becomes weaker as the value increases.

<< Embodiment 3 >>
An example of the radionuclide production apparatus of the third embodiment will be described with reference to FIG.

The radionuclide production apparatus of the third embodiment has the same configuration as the apparatus of the first embodiment, but is different from the first embodiment in that the circulation loop 21 is provided with the gas discharge port 40. By providing the discharge port 30, it is possible to release the gaseous nuclide generated by the decay of the radionuclide contained in the fluid 20. As a result, it is possible to suppress the inclusion of gas in the fluid 20, and the fluid 20 can be stably circulated by the pump 22. The details will be described below.

When Ra-226 is used as the raw material nuclide in the circulation loop for the radionuclide production solution, it undergoes alpha decay with a half-life of 1600 years and produces radon 222 (Rn-222). Rn-222 belongs to a rare gas element and is known to exist as a monatomic molecule gas in the standard state. For example, assuming that the solvent of the fluid 20 is water at 20 ° C., the solubility of Rn-222 in water is 24.5 ml per 100 ml, so that an amount of Rn-222 that is insoluble in water is generated in the circulation loop 21. In that case, it will exist as a gas in the fluid 20.

The pump 22 may not operate normally when a gas is mixed with the fluid 20. Further, since the volume of the gas is large, when the gas is mixed with the fluid 20, the amount of the raw material nuclide Ra-226 contained in the fluid 20 in the region irradiated with the braking radiation 12 is reduced. Therefore, the amount of Ra-225 produced from the raw material is reduced.

Therefore, in the present embodiment, the gas contained in the fluid 20 is discharged by providing the discharge port 40 in the circulation loop 21. As a result, the above-mentioned inconvenience caused by the gas being mixed in the fluid 20 can be eliminated, and a desired nuclide can be stably produced.

It should be noted that the gas is not always discharged from the discharge port 40, and may be periodically or irregularly depending on the amount of gas nuclides produced such as Rn-222 and the solubility of the gas in the solution of the fluid 20. It may be released at a regular release timing.

<< Embodiment 4 >>
An example of the radionuclide production apparatus of the fourth embodiment will be described with reference to FIGS. 5 and 6.

The radionuclide production apparatus of the fourth embodiment has the same configuration as that of the first embodiment, but all or a part 23 of the piping of the circulation loop 21 is made of the material of the braking radiation target 11, and the braking radiation target 11 It is different from the first embodiment in that it also serves as. The radiation generator 50 irradiates the electron beam 10 toward the piping of the circulation loop 21 made of a material that generates braking radiation. As a result, braking radiation 12 is generated from the piping, and the fluid 20 flowing inside the circulation loop 21 is irradiated.

A metal having a large atomic number such as tungsten or platinum can be used as the material constituting all or part of the pipe 23 that also serves as the braking radiation target 11 of the circulation loop 21.

In this way, since a part of the piping of the circulation loop 21 also serves as the braking radiation target 11, the distance between the position where the braking radiation 12 is generated (target 11) and the raw material nuclide of the fluid 20 is shortened. As a result, the intensity of the braking radiation 12 irradiated to the raw material nuclide is increased, so that the amount of the desired radionuclide (for example, Ra-225) produced is increased.

In the braking radiation target 11, the energy of the electron beam 10 is lost, so that the temperature of the target 11 rises, but since the fluid 20 circulates, the target 11 can be cooled by the fluid 20. That is, the fluid 20 cools the target 11 by receiving heat by heat conduction at a position in contact with the braking radiation target 11 and dissipating the heat received in the region of the circulation loop 21 which does not also serve as the target 11. be able to.

Further, a cooling unit 24 for cooling the fluid 20 may be arranged in the middle of the circulation loop 21. As a result, the braking radiation target 11 can be efficiently cooled by the fluid 20.

Further, instead of the cooling unit 24, a temperature adjusting unit having both heating and cooling functions may be arranged. As a result, the temperature adjusting unit 24 heats or cools the fluid 20 according to the heat generation temperature of the braking radiation target 11, and the temperature at which the radionuclide production solution does not vaporize or the temperature at which the solubility of the raw material nuclide is maximized. Can be kept in.

Further, as shown in FIG. 5, a control unit 60 that controls the temperature adjusting unit 24 and the pump 22 may be arranged. As shown in FIG. 6, the control unit 60 controls the operation and stop times of the pump 22 and the flow rate during operation. Further, the control unit 60 controls the operation of the temperature control unit 24 to heat or cool the fluid 20. In this way, the control unit 60 can adjust the temperature of the fluid 20 to a predetermined temperature range by controlling both the pump 22 and the temperature control unit 24.

Further, the control unit 60 may adjust the flow rate of the pump 22 according to the amount of radionuclides to be taken out from the separation device 30. That is, when it is desired to reduce the amount of radionuclides taken out from the separation device 30, the control unit 60 reduces the flow rate of the pump 22. By adjusting the flow rate of the pump 22 in this way, the production amount can be controlled.

<< Embodiment 5 >>
An example of the radionuclide production apparatus of the fifth embodiment will be described with reference to FIG.

The radionuclide production apparatus of the fifth embodiment has the same configuration as the apparatus of the first embodiment, but differs from the first embodiment in that a plurality of radiation generators 50 are provided around the circulation loop 21. .. Each of the plurality of radiation generators 50 irradiates the circulation loop 21 with radiation. For example, when the circulation loop 21 is irradiated with braking radiation from two radiation generators 50 having the same structure as shown in FIG. 7, it is doubled as compared with the case where one radiation generator 50 of FIG. 1 is used. Since the amount of radionuclides (for example, Ra-225) can be produced, the production efficiency can be improved.

Further, since the apparatus of the present embodiment 5 includes a plurality of radiation generators 50, even if one radiation generator 50 fails, the production can be continued using the other one, so that the apparatus can be generated. The risk of not being able to produce nuclides at all can be reduced.

Further, by combining the configurations of the present embodiment and the fourth embodiment, all or a part of the piping of the circulation loop 21 is made of a metal having a large atomic number such as tungsten or platinum, and a plurality of piping of the circulation loop 21 is provided. It may be configured to be also used as the braking radiation target 11 at a location.

<< Embodiment 6 >>
An example of the radionuclide production apparatus of the sixth embodiment will be described with reference to FIG.

The radionuclide production apparatus of the sixth embodiment has the same configuration as the apparatus of the first embodiment, but is implemented in that the circulation loop 21 is provided with a detour circuit 25 for bypassing the separation device 30 and a flow path switcher 27. It is different from Form 1.

Since the radionuclide production apparatus of the first embodiment has a configuration in which the fluid 20 passes through the separation device 30 each time it circulates in the circulation loop 21, the radionuclide is always taken out from the separation device 30 during the operation of the apparatus. On the other hand, in the radionuclide production apparatus of the sixth embodiment, the detour circuit 25 is provided, and the flow path switch 27 can select whether to flow the fluid 20 through the detour circuit 25 or the separation device 30. As a result, even during the operation of the device, the radionuclide is not taken out when the fluid 20 is passed through the detour 25, and the radionuclide is taken out only when the fluid 20 is passed through the separation device 30. Therefore, according to the radionuclide production apparatus of the sixth embodiment, the timing of taking out the radionuclide can be controlled. For example, Ac-225 can be produced from the raw material Ra-226 as in the following example.

Ra-225 produced by irradiating the fluid 20 containing Ra-226, which is the raw material, with braking radiation 12, undergoes beta decay with a half-life of 14.8 days and becomes the progeny nuclide Ac-225. FIG. 9 shows an example of the amounts of Ra-225 and Ac-225 in the fluid 20 when the fluid 20 containing Ra-226 is irradiated with the braking radiation 12 for 20 hours, which is shorter than the half-life of Ra-225. Shown. In the example of FIG. 9, since the irradiation time of the braking radiation 12 is sufficiently shorter than the half-life of Ra-225, the amount of Ra-225 depends on the time while the braking radiation 12 is being irradiated. It increases and gradually decreases because it undergoes beta decay with a half-life of 14.8 days after the end of irradiation. On the other hand, Ac-225 increased after the increase of Ra-225 while being irradiated with the braking radiation 12, and increased in response to the gradual decrease of Ra-225 due to beta decay even after the irradiation was completed. It reaches its maximum in about 428 hours, but decreases with a half-life of 10.0 days as it changes to the progeny nuclide Fr-221.

At this time, in the radionuclide production apparatus of the present embodiment, the flow path switch 27 is set so that the fluid 20 is passed through the separation apparatus 30 during and after the irradiation, and Ac-225 is continuously separated and taken out. It can be taken out from the part 31.

Further, as shown in FIG. 10, the radionuclide production apparatus of the present embodiment can intermittently take out Ac-225.

FIG. 10 shows Ra-225 and Ac- in the fluid 20 when the fluid 20 containing Ra-226 is irradiated with the braking radiation 12 for 20 hours, which is shorter than the half-life of Ra-225, as in FIG. An example of the amount of 225 is shown. The increase and decrease of Ra-225 in FIG. 10 are the same as in FIG. Further, in FIG. 10, it is the same as in FIG. 9 that Ac-225 increases and reaches the maximum amount about 428 hours after the irradiation of the braking radiation 12.

In the example of FIG. 10, the fluid 20 is passed through the detour 25 by the flow path switcher 27 for 428 hours after the irradiation of the braking radiation 12, but the fluid 20 is separated by the flow path switcher 27 at 428 hours after the irradiation. It is passed through the apparatus 30 and all Ac-225 of the fluid 20 in the circulation loop 21 is taken out (first separation and purification).

After the first take-out, the fluid 20 is flowed to the detour 25 by the flow path switch 27, or the circulation of the circulation loop 21 is stopped. Ac-225 is generated by the beta decay of Ra-225 already generated in the fluid 20 even if the fluid 20 is not irradiated with the braking radiation 12, so that it increases again as shown in FIG. Approximately 428 hours after the first removal, the maximum amount is reached again. Therefore, in the example of FIG. 10, the fluid 20 is flowed through the separation device 30 by the flow path switch 27, and all Ac-225 of the fluid 20 in the circulation loop 21 is taken out (second separation and purification).

After the second withdrawal, the fluid 20 is flowed through the detour 25 by the flow path switch 27, or the circulation of the circulation loop 21 is stopped, and about 428 hours after the second withdrawal, the fluid 20 is passed by the flow path switch 27. Is flowed through the separation device 30, and all Ac-225 of the fluid 20 in the circulation loop 21 is taken out (third separation and purification).

As described above, in the apparatus of the sixth embodiment, it is possible to continuously take out Ac-225 after irradiating the braking radiation 12, or to take out Ac-225 intermittently.

In the radionuclide production apparatus of the sixth embodiment, the radiation generator 50 is not required while the Ac-225 is continuously or intermittently taken out after the braking radiation 12 is irradiated, as shown in FIG. By moving the circulation loop 21 from the front of the radiation generator 50 and installing another raw material nuclide 15 or another circulation loop 21 in the moved portion, another nuclide or a radionuclide in the other circulation loop 21 is installed. Can be manufactured. The form of the other raw material nuclide 15 may be solid or liquid.

1 ... electron beam accelerator, 10 ... electron beam, 11 ... braking radiation target, 12 ... braking radiation, 15 ... other raw material nuclei, 20 ... fluid, 21 ... circulation loop (circulation path), 22 ... pump, 23 ... piping Part where the target material is used as the material, 24 ... Cooling part, 25 ... Detour, 30 ... Separator, 31 ... Extraction part, 40 ... Discharge port

Claims

A circulation path that circulates the fluid containing raw materials,
A radiation generator that irradiates at least a part of the circulation path to generate a first radionuclide from the raw material.
A fluid containing at least a part of the first radionuclide and the second radionuclide generated from the first radionuclide is extracted from the fluid circulating in the circulation path, and the remaining raw material is contained. A radionuclide production apparatus comprising a separation apparatus for returning the fluid to the circulation path.
The radionuclide production apparatus according to claim 1, wherein the radiation generator includes an electron beam accelerator that emits an accelerated electron beam and braking radiation at a position where the electron beam emitted from the electron beam accelerator is irradiated. A radionuclide production apparatus comprising a holding portion for holding a target for radionuclide, which irradiates the fluid with braking radiation generated from the target for braking radiation irradiated with the electron beam.
The radioactive nuclei production apparatus according to claim 1, wherein the fluid is a solution in which the raw material is dissolved in a solvent, a dispersion solution in which the raw material is dispersed in a solvent, and a dispersion gas in which the raw material is dispersed in a gas. A radioactive nuclei species production apparatus characterized in being one of the following.
The radionuclide production apparatus according to claim 1, wherein a part of the circulation path has a region in which the fluid flows in a linear direction.
A radionuclide production apparatus, characterized in that the radiation generator is arranged so that the central axis of radiation emitted by the radiation generator passes through the linear region of the circulation path.
The radionuclide production apparatus according to claim 1, wherein a discharge port for discharging gaseous nuclides generated by the decay of the radionuclide contained in the fluid is provided in the circulation path. A radionuclide production device characterized by this.
The radionuclide production apparatus according to claim 1, wherein at least a part of the circulation path is made of a material that generates braking radiation by being irradiated with an electron beam.
The radiation generator is an electron beam accelerator that emits an accelerated electron beam, emits the electron beam toward the circulation path made of a material that generates the braking radiation, and a fluid flowing through the circulation path. A radionuclide production apparatus characterized by irradiating a radionuclide.
The radionuclide production apparatus according to claim 1, further comprising a pump provided in the circulation path and a control unit for controlling the pump.
The radionuclide production apparatus, wherein the control unit adjusts at least one of a pump operation and stop time and a flow rate during pump operation.
The radionuclide production apparatus according to claim 1, wherein the circulation path is provided with a cooling unit for cooling the fluid.
The radionuclide production apparatus according to claim 2, wherein the radiation generators are a plurality of units, and each of the radiation generators irradiates different parts of the circulation path with braking radiation. Radionuclide production equipment.
The radionuclide production apparatus according to claim 1, wherein the circulation path is provided with a detour circuit that bypasses the separation device.
While the fluid containing the raw material is circulated along the circulation path, the fluid is irradiated with radiation in the middle of the circulation path to generate a first radionuclide from the raw material in the fluid.
While circulating the fluid along the circulation path, a substance containing at least a part of the first radionuclide and the second radionuclide generated from the first radionuclide is taken out from the fluid. , A method for producing a radionuclide, which comprises returning a fluid containing the remaining raw materials to the circulation path and circulating the fluid.
The radionuclide production method according to claim 11, wherein the radiation is bremsstrahlung radiation generated by irradiating a target with accelerated electrons.
The method for producing a radionuclide according to claim 11, wherein the raw material is radium-226 (Ra-226), the first radionuclide is radium 225 (Ra-225), and the second A method for producing a radionuclide, characterized in that the radionuclide is actinium-225 (Ac-225).
The method for producing a radionuclide according to claim 11, wherein the raw material is molybdenum 100 (Mo-100) or molybdenum trioxide 100, and the first radionuclide is molybdenum 99 (Mo-99). A method for producing a radionuclide, wherein the second radionuclide is technetium-99m (Te-99m).
The method for producing a radioactive nuclei according to claim 11, wherein the fluid is a solution in which the raw material is dissolved in a solvent, a dispersion solution in which the raw material is dispersed in a solvent, and a dispersion gas in which the raw material is dispersed in a gas. A method for producing a radioactive nuclei, which is characterized by being one of the following.